1. Field of the Invention
This invention relates to industrial vaults.
2. Description of the Related Art
Industrial vaults are widely used as locations for junctions of electrical cables, pipes, and conduits for telephone and electrical power distribution. Typically, vaults are made of concrete and comprise a bottom, sides, and a top. Vaults can include access ports for workers to gain entrance to the vault to install and/or repair the components in the vault. Vaults are cast in forms, or molds, typically made of steel, that define interior and exterior surfaces of the vault. Because vaults are typically placed underground, the walls must have sufficient strength to withstand the vertical and lateral forces exerted by the ground surrounding the vault. The mechanical strength of vaults is increased typically by using reinforcing rods or xe2x80x9crebarxe2x80x9d arranged to form a cage. A rebar cage typically includes vertical and horizontal members linked together with wire. A mold surrounds the cage and concrete is poured into the mold, forming a cast vault body, or xe2x80x9ccore.xe2x80x9d Other features, including openings and cable rack attachment points are typically made at the time of casting the vault body. After casting, cable racks are conventionally attached to the interior surfaces of vaults at attachment points, termed herein xe2x80x9ccable rack inserts.xe2x80x9d Cable rack inserts are devices that are cast in the vault body and provide a channel for the insertion of a screw used to hold the cable rack in place in the vault. Cable hooks are attached to the cable racks and are points of attachment of cables, junction boxes, xe2x80x9cTxe2x80x9d junctions, grounding straps, other articles, etc.
Installation of prior art cable racks typically require the casting of a cable rack insert in the body of the vault during its manufacture. Placement of prior art cable rack inserts involves several steps. First, for metal inserts, a worker must enter the form and bolt the cable rack insert into place within the form. Next, the body of the vault, or core is cast. Then, the metal insert must be unbolted from the form, the core is then removed and finally, the cable rack assembly must be bolted into place. In another type of prior art insert, described in U.S. Pat. No. 3,982,363, the cable rack insert is made of plastic and has a weak point, so that after casting of the core the weak point breaks as the core is removed from the mold, leaving the insert in place in the core. This method results in a plastic cable rack insert which is fragile and can be subject to damage or destruction upon bolting the cable rack to the insert. This problem can be especially severe if galvanized bolts are used.
Electrical cables, pipes and conduits typically are inserted into a vault through openings in the side of the vault via terminator plates. Terminator plates and vault openings are typically formed at the time of formation of the vault structure. FIG. 1 depicts a prior art vault as described in U.S. Pat. No. 3,731,448 (incorporated herein fully by reference) having cast-in terminator plates and vault openings. The body of the vault is shown cut-away to reveal the reinforcing bars and duct terminator 19 having holes 33 therethrough. The duct terminator of the prior art vault is positioned within the mold, and is cast into the core. FIG. 2 depicts another example of a prior art terminator plate as described in U.S. Pat. No. 4,075,803 (incorporated herein fully by reference). In this device, the duct terminator is split so that the terminator can be placed around existing cables without requiring the cable connections to be severed. Yet another type of prior art device is depicted in FIG. 3. The device is placed in the form and is cast into the body of the vault. Upon removal of the vault from the form, the device shown in FIG. 3 is a conduit permitting wiring to enter the vault.
In the prior art terminator plates, the the plates and the vault openings are typically located on the basis of either site requirements or specific customer requests. Once manufactured, the configuration of the openings and/or terminator plates is fixed; modifications can be difficult to accomplish without replacing the entire vault. Moreover, neither site-specific nor customer-specific manufacture lend themselves to assembly line production methods. Thus, the cost of the vault is high and the time lapse between customer order and delivery of the finished vault can be undesirably long.
Therefore, prior art vaults can have substantial disadvantages. They are not easily manufactured using assembly line methods, they require more time to manufacture, they expose workers to unnecessary risks, and once made, the configurations are fixed which makes modifications difficult. Moreover, cast-in terminator plates are prone to leak at the concrete-terminator plate boundaries, allowing unwanted substances including water to gain access to the vault. The introduction of such substances increases the likelihood of short circuiting of electrical components, contamination of devices and corrosion of devices within the vault.
The present invention, roughly described, provides for a vault having thin-walled knock-outs formed at desired locations in the walls of the vault. In some embodiments of this invention, thin-walled knock-outs are placed in arrays on different surfaces of the vault, including the sides, ends and the top, forming xe2x80x9csegmented knockouts.xe2x80x9d The knock-outs can have reinforced xe2x80x9cribsxe2x80x9d between knock-outs and can have surfaces that are adapted to receive terminator plates of varying dimensions and configurations. The ribs can be thinner than the major structural portions of the vaults, thereby conserving materials and decreasing the weight of the vault.
The reinforcing members of thin ribs can advantageously be placed in a plane offset from the plane of rebar used to reinforce the major structural portions of the vault, such as exterior corners and sides. Because mechanical strength resisting positive and negative loads is maximized by placing reinforcing members in the middle of a reinforced structure such as a wall, an offset pattern of reinforcing members can provide stronger vaults. In one embodiment, the planes of the major structural members and the thin ribs is different; therefore, the reinforcing members do not meet each other. However, they can be attached to one another using special xe2x80x9crebar support mounting bracketsxe2x80x9d or xe2x80x9csupport brackets.xe2x80x9d Rebar cages are configured using support brackets to permit the joining of rebar members of the segmented knock-outs to the rebar of other structural supporting members, making a monocoque structure, which has greater inherent strength than simple prior art cages.
In one embodiment, vaults have pre-installed cable racks, which can be incorporated into a cage prior to casting the vault. In certain embodiments, the cable racks can be electrically connected to support brackets, which can be electrically connected to the rebar cage. Grounding clamps can be provided on the cable racks so that electrical equipment and connections within the vault can be easily grounded. Thus, there is no requirement for a separate ground strap to protect electrical components.
Vaults can be transported to an installation site and placed at a desired location before locations of access points to the vault are selected. Once sited and placed, access locations to the vault""s interior can be selected, knock-outs at those locations can be removed, and terminator plates can be installed. Terminator plates can have an array of separate conduit ports, each port providing a possible point of access to the interior of the vault In alternative embodiments, terminator plates can be pre-installed and subsequently, a desired conduit port in the terminator plate can be selected, an occluding diaphragm can be perforated and a cable channel can be formed. Therefore, the vaults of this invention provide for on-site selection of access points, and can permit multiple modifications of the vault at the site.
In other embodiments of this invention, terminator plates are provided that can be easily installed and can provide tight seals thereby diminishing the contamination of the vault with unwanted materials, including water. In some of these embodiments, the terminator plates comprise two portions. A first portion includes an inside terminator plate that has one or more conduit ports and is placed in an interior surface of the knock-out perforation. A second portion includes an exterior seal plate placed on the exterior surface of the knock-out hole. Segments of the terminator plates can join each other and can be bonded with solvent cement or other adhesive known in the art, providing a tight seal between inside and exterior elements. The junctions between terminator plates and a vault surface can be sealed after installation of terminator plates by injecting a sealant between plate elements and the vault material. After sealant injection, a seal between the terminator plate and the vault is formed that is tighter than possible with cast-in terminator plates.
Alternative designs and configurations of terminator plates are contemplated. In certain embodiments, terminator plates can have an array of locations for attachment of conduit ports. If desired, conduit ports can be made with a diaphragm occluding the lumen. Selected conduit ports can have the diaphragms perforated for insertion of conduits and electric cables. In some embodiments of this invention, multiple conduit ports and conduits can be used to create a number of access points to the vault. Conduits can be attached to the conduit ports and sealed in place, thereby forming a continuous, protected path for electrical wires entering and/or leaving the vault. Cables inside a vault can then be attached to cable racks via cable hooks, and connections, junctions boxes, and other electrical devices can be installed.
The configuration of the vault can be adapted for individualized uses. When it is desirable to provide openings on the top of a vault, vault tops can be provided having both personnel access ports and panels of segmented knockouts.
In other embodiments, it can be desirable to provide a xe2x80x9cUxe2x80x9d-shaped vault having a flat top. Such embodiments can be connected end-to-end, thereby providing a channel or xe2x80x9ctrenchxe2x80x9d of any desired length. Such long vaults can be desirable for electrical power transmission. High-tension electrical cables can be laid within the vault and the vault can be sealed using a flat top. By providing segmented knock-outs and terminator plates of this invention, junctions between the power transmission cable can be provided where desired, thus permitting xe2x80x9cTxe2x80x9d junctions. Such uses include providing lateral electrical supplies to structures along the power transmission route.
By employing design features of this invention, the thickness of the walls can be minimized, while providing adequate strength of each structural member, thus decreasing material cost and overall weight of the vault. Using the designs of this invention, the total amount of material, such as concrete, can be decreased by approximately twenty five to fifty percent. The designs of vaults of this invention also permit more rapid manufacture, in certain embodiments, decreasing the time required by as much as fifty percent. Moreover, the designs and methods of this invention can provide convenient pre-manufactured vaults made in assembly line processes, and can permit the selection of the locations of terminator plates, conduits, and cables to be made on site. These features and others increase the flexibility of installation of electrical and other components.